Backlight units and display devices including the same

ABSTRACT

A display device includes a display panel which displays an image, a backlight unit which supplies the display panel with light, an upper cover, and a lower cover. The upper and lower covers accommodate the display panel and the backlight unit. The backlight unit includes light guide plates spaced apart from each other, a light source part, an optical member and an optical diffusion member overlapping a space between the light guide plates. The optical diffusion member includes a diffusing part and a supporting part. The diffusing part faces the optical member, overlaps the space between the light guide plates, and diffuses light emitted from the light source part toward the optical member through the space between the light guide plates. The supporting part protrudes from a surface of the diffusing part which is opposite to the optical member, and is in a space between the light sources.

This application claims priority to Korean Patent Application No.10-2011-0073286, filed on Jul. 22, 2011, and all the benefits accruingtherefrom under 35 U.S.C. §119, the entire contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The invention herein relates to a backlight unit and a display deviceincluding the backlight unit, and more particularly, to a backlight unitincluding light guide plates, and a display device including thebacklight unit.

(2) Description of the Related Art

Since display devices including a liquid crystal display (“LCD”) panelor an electrophoretic display panel (“EDP”) to display an image arenon-emissive devices having no light source, they need a backlight unitfor supplying light thereto.

Such backlight units include a light source for emitting light, and alight guide plate for guiding the light from the light source to adisplay panel. If necessary, the light guide plate may be provided inplurality.

However, in this case, since the light source is disposed between thelight guide plates, light emitted from the light source may leak upwardthrough a space between the light guide plates. Furthermore, the leakinglight may degrade displaying quality of the display panel.

BRIEF SUMMARY OF THE INVENTION

The invention provides a backlight unit and a display device includingthe backlight unit, to thereby improve displaying quality of the displaydevice.

Embodiments of the invention provide backlight units including aplurality of light guide plates, a light source part, an optical member,and an optical diffusion member.

Each of the light guide plates includes a light incident surface throughwhich light is incident, and a light emitting surface through which thelight is guided and emitted, and the light guide plates are spaced apartfrom each other with the light incident surfaces facing each other.

The light source part disposed in a space between the light guideplates, and includes a plurality of light source units each includinglight sources spaced apart from each other, and at least one printedcircuit board on which at least one of the light source units is mountedNeighboring light sources emit light in opposite directions.

The optical diffusion member includes a diffusing part disposed over thespace between the light guide plates to diffuse light that is emittedfrom the light sources, leaks through the space between the light guideplates, and propagates toward the light emitting side of the light guideplates, and at least one supporting part protruding from the diffusingpart in a direction opposite to the light emitting side of the lightguide plates, and inserted in a space between the light sources.

In some embodiments, the diffusing part may include a reflective filmattached thereto on a surface facing the optical member.

In other embodiments, the reflective film may include micro lenses on asurface facing the optical member, or may include diffusion beadstherein.

In still other embodiments, the diffusing part may include at least oneprotrusion protruding toward the optical member to space the light guideplate apart from the optical member.

In even other embodiments, the diffusing part may have a dome or convexshape.

In yet other embodiments, the backlight units may further include alight guide plate supporting member that is disposed under the spacebetween the light guide plates, and is coupled to the optical diffusionmember to support the light guide plates.

In further embodiments, the optical diffusion member may include athrough hole passing through the diffusing part, the light guide platesupporting member may include a coupling hole corresponding to thethrough hole, and the backlight unit may further include a couplingmember inserted in the through hole and the coupling hole to couple theoptical diffusion member to the light guide plate supporting member.

In still further embodiments, the optical diffusion member may include acatching protrusion at a lower end of the supporting part, the catchingprotrusion may have a greater area than that of the supporting part withrespect to a cross-section perpendicular to a direction of light emittedfrom the light guide plates, and the light guide plate supporting membermay be disposed under the light guide plate, and include anaccommodating recess in which the catching protrusion is inserted andfixed.

In other embodiments of the invention, display devices include: adisplay panel displaying an image; the backlight unit supplying thedisplay panel with light; an upper cover; and a lower cover. The upperand lower covers accommodate the display panel and the backlight unit.

In some embodiments, the optical diffusion member may include a throughhole passing through the diffusing part, the lower cover may include acoupling hole corresponding to the through hole, and the display devicemay further include a coupling member inserted in the through hole andthe coupling hole to couple the optical diffusion member to the lightguide plate supporting member.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures are included to provide a further understandingof the invention, and are incorporated in and constitute a part of thisspecification. The drawings illustrate exemplary embodiments of theinvention and, together with the description, serve to explainprinciples of the invention. In the figures:

FIG. 1 is an exploded perspective view illustrating an exemplaryembodiment of a display device according to the invention;

FIG. 2 is an exploded perspective view illustrating a coupling structureof a light source part, light guide plates, an optical diffusion member,and an optical member of FIG. 1;

FIGS. 3A and 3B are perspective views illustrating the light source partof FIG. 2;

FIGS. 4A to 4C are perspective views illustrating exemplary embodimentsof optical diffusion members applicable to a display device according tothe invention;

FIGS. 5A and 5B are enlarged views illustrating exemplary embodiments ofportion B of FIG. 4A;

FIG. 6 is a cross-sectional view illustrating an exemplary embodiment ofa coupling structure of an optical diffusion member, light guide plates,a light source part, and an optical member according to the invention;and

FIGS. 7 to 9 are cross-sectional views illustrating exemplaryembodiments of backlight units of display devices according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, theelement or layer can be directly on, connected or coupled to anotherelement or layer or intervening elements or layers. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. As used herein, connected mayrefer to elements being physically and/or electrically connected to eachother. Like numbers refer to like elements throughout. As used herein,the term “and/or” includes any and all combinations of one or more ofthe associated listed items.

It will be understood that, although the terms first, second, third,etc., may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsare only used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the invention.

Spatially relative terms, such as “lower,” “under,” “above,” “upper” andthe like, may be used herein for ease of description to describe therelationship of one element or feature to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation, in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “lower” or “under”relative to other elements or features would then be oriented “above”relative to the other elements or features. Thus, the exemplary term“below” can encompass both an orientation of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view illustrating an exemplaryembodiment of a display device according to the invention. FIG. 2 is anexploded perspective view illustrating a coupling structure of a lightsource part, light guide plates, an optical diffusion member, and anoptical member of FIG. 1. FIGS. 3A and 3B are perspective viewsillustrating the light source part of FIG. 2.

Referring to FIGS. 1 to 3B, a display device 500 according to theexemplary embodiment includes a display panel 100, a backlight unit 200,an upper cover 310, and a lower cover 320.

The display panel 100 may be any one of various display panels such as aliquid crystal display (“LCD”) panel and an electrophoretic displaypanel (“EDP”). In the exemplary embodiment, a LCD panel is exemplifiedas the display panel 100.

The display panel 100 has a rectangular plate shape with short and longsides. The display panel 100 includes an array substrate 110, anopposite substrate 120 facing the array substrate 110, and a liquidcrystal layer (not shown) disposed between the array substrate 110 andthe opposite substrate 120.

The array substrate 110 may include a plurality of pixels (not shown) ina matrix shape. In an exemplary embodiment, each pixel may include agate line (not shown) extending in a first direction, e.g., in adirection parallel to a side of the array substrate 110, a data line(not shown) extending in a second direction crossed with the firstdirection and electrically insulated from the gate line, and a pixelelectrode (not shown). Each pixel may include a thin film transistor(not shown) that is electrically connected to the gate line, the dataline, and the pixel electrode. Each thin film transistor switches adriving signal that is provided to the corresponding pixel electrode.Driver integrated circuits (“ICs”) 130 may be disposed at a side of thearray substrate 110. The driver ICs 130 receive various signals, andoutput signals for driving the display panel 100, in response to variousinput control signals.

The opposite substrate 120 may include a red, green and blue (“RGB”)color filter (not shown) and a common electrode (not shown) on a surfacethereof The RGB color filter uses light to create a predetermined color.The common electrode is disposed on the RGB color filter, and is opposedto the pixel electrode. The RGB color filter may be formed through athin film process. The opposite substrate 120 includes the RGB colorfilter in the exemplary embodiment, but is not limited thereto. In analternative embodiment, for example, the RGB color filter may bedisposed on the array substrate 110.

The liquid crystal layer has a specific arrangement direction accordingto an electric field formed between the pixel electrode and the commonelectrode, to thereby adjust the transmissivity of light emitted fromthe backlight unit 200, so that the display panel 100 can display animage.

The backlight unit 200 is disposed under and overlapping the displaypanel 100. The backlight unit 200 includes a plurality of light guideplates 210, at least one light source part 220, an optical member 230, areflective sheet 240, and an optical diffusion member 250 for diffusinglight from the light source part 220 leaking between adjacent lightguide plates 210.

The light guide plates 210 are adjacent to each other and both disposedunder the display panel 100, and guide light emitted from the lightsource part 220 to the display panel 100. The light guide plates 210 arespaced apart from each other in a plan view of the displace device 500such that side surfaces thereof face each other. Each of the light guideplates 210 includes a light incident surface 211 through which light isincident, and a light emitting surface 212 emitting the light incidentthrough the light incident surface 211. The light emitting surface 212may face an incident surface of the display panel 100.

The light source part 220 is disposed between the light guide plates210, and includes a plurality of light source units L.U including lightsources 221 and 222 spaced apart from one another, and at least oneprinted circuit board 223 on which the light source units L.U aremounted. The light sources 221 and 222 of the light source unit L.U emitlight in opposite directions to the light guide plates 210,respectively, as indicated by the dotted line arrows in FIGS. 3A and 3B.In one embodiment, for example, referring to FIG. 3A, the light sourceunits L.U may be mounted on a single board as the printed circuit board223, to thereby constitute the light source part 220. Alternatively,referring to FIG. 3B, the light source units L.U may be mounted on aplurality of separate boards as a plurality of printed circuit boards223, respectively, to thereby constitute the light source part 220.

One of the light sources 221 and 222, which emits light to any one ofthe light guide plates 210, may be referred to as a first light source(also denoted by 221), and the other of the light sources 221 and 222,which emits light to the other of the light guide plates 210, may bereferred to as a second light source (also denoted by 222). In thiscase, power may be separately applied to the first and second lightsources 221 and 222 to perform a local dimming operation on thebacklight unit 200.

The optical diffusion member 250 includes a diffusing part 251 andsupporting parts 252, and diffuses light from the light sources 221 and222 leaking between the light guide plates 210.

The optical member 230 is disposed between the display panel 100 and theplurality of light guide plates 210. That is, the optical member 230 isdisposed at the side of the display panel 100 to which light is emittedfrom the light guide plates 210, e.g., is disposed over the lightemitting surfaces 212 of the light guide plates 210. The optical member230 controls light emitted from the light guide plates 210. The opticalmember 230 may include a diffusion sheet, a prism sheet, and/or aprotective sheet, which are sequentially stacked on the light guideplates 210.

The diffusion sheet diffuses light emitted from the light source part220. The prism sheet collects the light, diffused by the diffusionsheet, in a direction perpendicular to a plane of the display panel 100disposed over the prism sheet. Most of the light passing through theprism sheet is perpendicularly incident to the display panel 100. Theprotective sheet is disposed on the prism sheet. The protective sheetprotects the prism sheet from external shock.

In the exemplary embodiment embodiment, the optical member 230 includesa single sheet as each of the diffusion sheet, the prism sheet, and theprotective sheet, but is not limited thereto. Thus, at least one of thediffusion sheet, the prism sheet, and the protective sheet may beprovided in plurality to form the optical member 230, or one of thediffusion sheet, the prism sheet, and the protective sheet may beremoved.

The reflective sheet 240 reflects otherwise wasted light back to thedisplay panel 100, and is disposed under the light guide plates 210. Thereflective sheet 240 includes a light reflecting material. Thereflective sheet 240 is disposed on the lower cover 320 to reflect lightemitted from the light source part 220. Thus, the reflective sheet 240increases the amount of light provided to the display panel 100.

The upper cover 310 is disposed over the display panel 100, and has ashape corresponding to the shape of the display panel 100. The uppercover 310 includes an upper surface 312 having a display window 311exposing the display panel 100 and supporting an edge of the top surfaceof the display panel 100, and a side surface 314 extending from theupper surface 312 toward the lower cover 320. Since the display panel100 has a rectangular plate shape, the side surface 312 of the uppercover 310 may include four side surfaces 314. The upper cover 310 iscoupled to the lower cover 320 to support the edge of the top surface ofthe display panel 100.

The lower cover 320 is disposed under the backlight unit 200. The lowercover 320 includes a bottom surface 322 having a shape corresponding tothe shapes of the display panel 100 and the backlight unit 200, and aside surface 324 extending upward toward the upper cover 310 from thebottom surface 322. Since the display panel 100 and the backlight unit200 have a tetragonal shape, the side surface 324 of the lower cover 320may have four side surfaces 324. The lower cover 320 has a space definedby the bottom surface 322 and the side surface 324, to therebyaccommodate the display panel 100 and the backlight unit 200. The lowercover 320 is coupled to the upper cover 310 to accommodate and supportthe display panel 100 and the backlight unit 200.

FIGS. 4A to 4C are perspective views illustrating exemplary embodimentsof optical diffusion members applicable to a display device according tothe invention. FIGS. 5A and 5B are enlarged views illustrating exemplaryembodiments of portion B of FIG. 4A. FIG. 6 is a cross-sectional viewillustrating an exemplary embodiment of a coupling structure of anoptical diffusion member, light guide plates, a light source part, andan optical member according to the invention.

Referring to FIG. 4A, the optical diffusion member 250 includes thediffusing part 251 and the supporting parts 252, and diffuses lightleaking between the light guide plates 210 from the light sources 221and 222.

The diffusing part 251 is disposed over and overlaps a space between theadjacent light guide plates 210. That is, the diffusing part 251 coversthe upper portion of the space between the light guide plates 210. Thediffusing part 251 diffuses light that leaks between the light guideplates 210 from the light sources 221 and 222, and that propagates inthe direction of light emitted from the light guide plates 210. That is,the diffusing part 251 diffuses light that leaks between the light guideplates 210 from the light sources 221 and 222, and that propagatestoward the display panel 100.

The diffusing part 251 has a tetragonal plate shape with short and longsides. The length of the long sides of the diffusing part 251 may beequal to or greater than the length of the space between the light guideplates 210. The length of the short sides of the diffusing part 251 maybe greater than the width of the space between the light guide plates210. In one embodiment, for example, the length of the short sides maybe from about 10 millimeters (mm) to about 15 mm.

The diffusing part 251 may include one or more protrusions 256 thatprotrude from a surface facing the optical member 230, to space theoptical member 230 a certain distance from the light guide plates 210.

The diffusing part 251 may be provided with a reflective film 255attached to the surface facing the optical member 230. The reflectivefilm 255 may include a translucent material, e.g., translucentpolyethylene terephthalate (“PET”). Referring to FIG. 5A, the reflectivefilm 255 may include micro lenses 255A protruding from the surfacefacing the optical member 230. Referring to FIG. 5B, the reflective film255 may include diffusion beads 255B therein. The micro lenses 255A andthe diffusion beads 255B diffuse light passing through the reflectivefilm 255 and not reflected by the reflective film 255, thereby emittingthe light toward the optical member 230.

The supporting parts 252 protrude from the diffusing part 251 in theopposite direction to the direction of light emitted from the lightguide plates 210. The supporting parts 252 are inserted between thelight sources 221 and 222 to support the diffusing part 251.

Referring to FIG. 4B, the diffusing part 251 of the optical diffusionmember 250 may have a tetragonal plate shape with short and long sidesin a dome shape that further protrude to the optical member 230 at animaginary line connecting the centers of the short sides to each other,than at the long sides. That is, the the optical diffusion member 250may be convex and protruded toward the optical member 230. Accordingly,the light guide plates 210 are spaced a certain distance from theoptical member 230, even if the supporting part 252 is not used.

Referring to FIG. 4C, the diffusing part 251 of the optical diffusionmember 250 may have a tetragonal plate shape with short and long sides,and include a protrusion 256 that protrudes from the surface facing theoptical member 230, to space the optical member 230 a certain distancefrom the light guide plates 210. The protrusion 256 may longitudinallyextend from one of the short sides of the diffusing part 251 to theother short side, to space the optical member 230 a certain distancefrom the light guide plates 210. The protrusion 256 in FIG. 4C is asingle, unitary, indivisible member, as compared to the plurality ofdiscrete protrusions 256 in FIG. 4A.

Other exemplary embodiments of backlight units, and display devicesincluding the backlight units, according to the invention will now bedescribed with reference to FIGS. 7 to 9. Like reference numerals referto like elements in FIGS. 1 to 6, and a description thereof will beomitted. Thus, the following embodiments will be described with respectto different parts as those of FIGS. 1 to 6.

Referring to FIG. 7, another exemplary embodiment of a backlight unit200 of a display device according to the invention includes a lightguide plate supporting member 257 coupled to an optical diffusion member250 to support light guide plates 210.

The light guide plate supporting member 257 may have a plate shape andbe disposed under a space between the light guide plates 210. That is,the light guide plate supporting member 257 is disposed opposite to thesurface of the light guide plates 210 facing the optical member 230, andcovers the space between the light guide plates 210.

A diffusing part 251 of the optical diffusion member 250 may include athrough hole 253, and the light guide plate supporting member 257 mayinclude a coupling hole 257A corresponding to and aligned with thethrough hole 253.

The light guide plate supporting member 257 is coupled to the opticaldiffusion member 250 through a coupling member 254 such as a screw orrivet inserted in the through hole 253, to thereby support the lightguide plates 210. That is, the diffusing part 251 and the light guideplate supporting member 257 support the light guide plates 210 with acoupling force between the light guide plate supporting member 257 andthe optical diffusion member 250. Thus, while the display device isused, a dislocation of the light guide plates 210 due to external shockcan be prevented.

Referring to FIG. 8, another exemplary embodiment of a backlight unit200 of a display device according to the invention may include acatching protrusion 252A disposed at the lower end of a supporting part252, and an accommodating recess 257B disposed in the upper portion of alight guide plate supporting member 257. The catching protrusion 252 aand the supporting part 252 collectively form a single, unitaryindivisible member.

With respect to a cross-section perpendicular to the direction of lightemitted from the light guide plates 210, the area of the catchingprotrusion 252A is greater than that of the supporting part 252.

The catching protrusion 252A may be inserted and accommodated in theaccommodating recess 257B.

Accordingly, in the backlight unit 200 including the optical diffusionmember 250 and the light guide plate supporting member 257, the opticaldiffusion member 250 can be coupled to the light guide plate supportingmember 257 without using a separate coupling member. That is, thecatching protrusion 252A of the optical diffusion member 250 is insertedand accommodated in the accommodating recess 257B of the light guideplate supporting member 257 to couple the optical diffusion member 250to the light guide plate supporting member 257.

Referring to FIG. 9, another exemplary embodiment of a backlight unit200 of a display device according to the invention may include acoupling hole 323 extended through a bottom surface 322 of a lower cover320 at a position corresponding to a supporting part 252 of an opticaldiffusion member 250. A coupling hole may also be extended through abottom surface of the reflective sheet 240. The optical diffusion member250 may include a through hole 253 passing through a diffusing part 251and the supporting part 252. A coupling member 254 such as a screw orrivet is inserted in the through hole 253 to fix the optical diffusionmember 250 to the lower cover 320.

Accordingly, the optical diffusion member 250 can more securely supportthe light guide plates 210 through the coupling member 254.

According to the embodiments, the backlight unit and the display deviceincluding the backlight unit include the optical diffusion member fordiffusing light leaking between the light guide plates. Thus, theleaking light, which is not guided by the light guide plates, can beprevented from degrading the displaying quality of the display device.

The above-disclosed subject matter is to be considered illustrative andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments, which fall withinthe true spirit and scope of the invention. Thus, to the maximum extentallowed by law, the scope of the invention is to be determined by thebroadest permissible interpretation of the following claims and theirequivalents, and shall not be restricted or limited by the foregoingdetailed description.

What is claimed is:
 1. A backlight unit comprising: a plurality of lightguide plates each including a light incident surface through which lightis incident, and a light emitting surface through which the light isguided and emitted, wherein the light guide plates are spaced apart fromeach other with the light incident surfaces facing each other; a lightsource part including a printed circuit board, and a plurality of lightsource units each including light sources spaced apart from each otherand on the printed circuit board, wherein the light source part is in aspace between the light guide plates; an optical member which faces alight emitting side of the light guide plates; and an optical diffusionmember including: a diffusing part which overlaps the space between thelight guide plates and diffuses light which is emitted from the lightsources, leaks through the space between the light guide plates, andpropagates toward the light emitting side of the light guide plates, anda supporting part which protrudes from the diffusing part in a directionopposite to the light emitting side of the light guide plates, and is ina space between the light sources, wherein adjacent light sourcesrespectively emit light in opposite directions.
 2. The backlight unit ofclaim 1, wherein the diffusing part comprises a reflective film on asurface thereof which faces the optical member.
 3. The backlight unit ofclaim 2, wherein the reflective film includes a translucent material. 4.The backlight unit of claim 2, wherein the reflective film comprisespolyethylene terephthalate.
 5. The backlight unit of claim 2, whereinthe reflective film comprises micro lenses on a surface thereof whichfaces the optical member.
 6. The backlight unit of claim 2, wherein thereflective film comprises diffusion beads therein.
 7. The backlight unitof claim 1, wherein the diffusing part has a tetragonal plate shape withshort sides and long sides.
 8. The backlight unit of claim 7, whereinthe diffusing part comprises a protrusion which protrudes toward theoptical member.
 9. The backlight unit of claim 8, wherein the protrusionlongitudinally extends from a first short side of the diffusing part toa second short side opposite the first short side of the diffusion part.10. The backlight unit of claim 7, wherein the diffusing part has aconvex shape which protrudes toward the optical member at an imaginaryline connecting centers of the short sides, further than at the longsides.
 11. The backlight unit of claim 1, further comprising a lightguide plate supporting member opposite to the diffusing part withrespect to the space between the light guide plates, wherein the lightguide plate supporting member is coupled to the optical diffusion memberand supports the light guide plates.
 12. The backlight unit of claim 11,wherein the optical diffusion member further includes a through holewhich passes through the diffusing part, the light guide platesupporting member comprises a coupling hole which overlaps the throughhole, and the backlight unit further comprises a coupling member whichextends through both the through hole and the coupling hole such thatthe optical diffusion member and the light guide plate supporting memberare coupled to each other.
 13. The backlight unit of claim 11, whereinthe optical diffusion member further includes a catching protrusion at alower end of the supporting part, the catching protrusion has a greaterarea than that of the supporting part with respect to a cross-sectionperpendicular to a direction of light emitted from the light guideplates, and the light guide plate supporting member is opposite to thediffusing part with respect to the space between the light guide plates,and comprises an accommodating recess in which the catching protrusionis inserted and fixed.
 14. A display device comprising: a display panelwhich displays an image; a backlight unit which supplies the displaypanel with light; an upper cover; and a lower cover, wherein the upperand lower covers accommodate the display panel and the backlight unittherein, wherein the backlight unit includes: a plurality of light guideplates each including a light incident surface through which the lightis incident, and a light emitting surface through which the light isguided and emitted, wherein the light guide plates are spaced apart fromeach other with the light incident surfaces facing each other; a lightsource part including a printed circuit board, and a plurality of lightsource units each including light sources spaced apart from each otherand on the printed circuit board, wherein the light source part is in aspace between the light guide plates; an optical member which faces alight emitting side of the light guide plates; and an optical diffusionmember including: a diffusing part which is between the optical memberand the space disposed between the light guide plates, wherein thediffusion part diffuses light that is emitted from the light sources andleaks through the space between the light guide plates, and a supportingpart which protrudes from the diffusing part in a direction opposite tothe light emitting side of the light guide plates, and is in a spacebetween the light sources, wherein adjacent light sources respectivelyemit light in opposite directions.
 15. The display device of claim 14,wherein the diffusing part comprises a reflective film on a surfacethereof which faces the optical member.
 16. The display device of claim15, wherein the reflective film includes a translucent material.
 17. Thedisplay device of claim 15, wherein the reflective film comprisespolyethylene terephthalate.
 18. The display device of claim 15, whereinthe reflective film comprises micro lenses on a surface thereof whichfaces the optical member.
 19. The display device of claim 15, whereinthe reflective film comprises diffusion beads therein.
 20. The displaydevice of claim 14, wherein the diffusing part has a tetragonal plateshape with short sides and long sides.
 21. The display device of claim20, wherein the diffusing part comprises a protrusion which protrudestoward to the optical member.
 22. The display device of claim 21,wherein the protrusion longitudinally extends from a first short side ofthe diffusing part to a second short side opposite to the first shortside of the diffusing part.
 23. The display device of claim 20, whereinthe diffusing part has a convex shape which protrudes toward the opticalmember at an imaginary line connecting centers of the short sides,further than at the long sides.
 24. The display device of claim 14,further comprising a light guide plate supporting member opposite to thediffusing part with respect to the space between the light guide plates,wherein the light guide plate supporting member is coupled to theoptical diffusion member and supports the light guide plates.
 25. Thedisplay device of claim 24, wherein the optical diffusion member furtherincludes a through hole which passes through the diffusing part, thelight guide plate supporting member comprises a coupling hole whichoverlaps the through hole, and the display device further comprises acoupling member which extends through both the through hole and thecoupling hole such that the optical diffusion member and the light guideplate supporting member are coupled to each other.
 26. The displaydevice of claim 25, wherein the coupling member comprises one of a screwand a rivet.
 27. The display device of claim 24, wherein the opticaldiffusion member further includes a catching protrusion at a lower endof the supporting part, the catching protrusion has a greater area thanthat of the supporting part with respect to a cross-sectionperpendicular to a direction of light emitted from the light guideplates, and the light guide plate supporting member is opposite to thediffusion part with respect to the space between the light guide plates,and comprises an accommodating recess in which the catching protrusionis inserted and fixed.
 28. The display device of claim 24, wherein theoptical diffusion member further includes a through hole which passesthrough the diffusing part, the lower cover comprises a coupling holewhich overlaps the through hole, and the display device furthercomprises a coupling member which extends through both the through holeand the coupling hole such that the optical diffusion member and thelight guide plate supporting member are coupled to each other.
 29. Thedisplay device of claim 28, wherein the coupling member comprises one ofa screw and a rivet.